VSEPR theory predicts molecular shapes based on electron pair repulsion around a central atom. It assumes that electron pairs will maximize their distance from each other to minimize repulsion. Molecular shapes include tetrahedral, trigonal pyramidal, bent, and linear based on the number of electron pairs. The theory uses Lewis structures to determine electron pairs from bonds and lone pairs, and predicts the shape that minimizes repulsion between these pairs.

1. Electron
Pair
Repulsion
Theory
Planar
triangular
Tetrahedral
Trigonal
pyramidal
Bent

2. VSEPR theory assumes that the shape of a
molecule is determined by the repulsion of
electron pairs.
Molecular Shape

3. VSEPR Theory
 Based on Electron Dot (Lewis structures)
 Theory predicts shapes of compounds
 abbreviated VSEPR
 VSEPR (pronounced “vesper”) stands for Valence Shell Electron Pair
Repulsion
 VSEPR predicts shapes based on electron pairs repelling (in bonds or by
themselves)
 Electrons around central nucleus repel each other. So,
structures have atoms maximally spread out

4. VSEPR overview
 Each shape has a name
(you will have to know these)
 Names of Shapes:
tetrahedral
trigonal pyramidal
Bent
Linear
trigonal planar

5. Triangular Planar
Tetrahedral
Trigonal pyramidal
Linear
Bent or V
Models

6. C
H
H
H
H methane, CH4
Bonds are all evenly spaced electrons
109.5°
C
H
H
H
H
Tetrahedral

7. N
H H
H
C
H
H
H
H
Less repulsion between the bonding pairs of electrons
.. ammonia
NH3
..
..
..
Trigonal
Pyramidal

8. C
H
H
H
H N
H H
H
O
H H
.. ..
..
109.5° (109.5°) 109.5° (107°) 109.5° (104.5°)
water, H2O

9. C
H
H
H
H N
H H
H
O
H H
.. ..
..

10. H
C
H H
H
N
H H
H
O
H H
Bent or V
2 unshared pairs of e’s
at top of O repel bonds
and force them to bend

11. Molecule Lewis Structure Number of
electron pairs
CH4
NH3
SHAPE
Tetrahedral
Trigonal
Pyramidal
4
4
(3 shared
1 lone pair)

12. Molecule Lewis Structure Number of
electron pairs
H2O
CO2
SHAPE
Bent or V
4
(2 shared
2 lone pairs)
2
Linear

13. Molecule Lewis Structure Number of
electron pairs
BeCl2
BF3
SHAPE
2
3
Linear
Trigonal
Planar